In February of 1988, F. Del Rector et al. (three authors in total) presented in New Orleans, La., United States of America, a technical paper entitled "Applications For The Aceoacetyl Functionality In Thermoset Coatings".
Briefly stated, these three authors reviewed some of the many, then-known methods and/or procedures for incorporating certain so-called "activated methylene" groups into different types or classes of resins, for purposes of preparing certain polymeric thermoset surface coatings and films, via a number of then-known crosslinking mechanisms.
More particularly, these authors discussed various well-known methods for reacting certain acetoacetyl-functional moiety-containing polymers with certain melamines, with certain isocyanates, with certain aldehydes, with certain diamines, and with certain other specified reactants via the so-called "Michael" reaction, to achieve desired crosslinking of the acetoacetyl-functional moiety.
For example, European Patent Application 0 326 723/A1 (assigned to Rohm & Haas Co.) discloses one such well-known method for producing a conventional "two-package" polymeric surface-coating composition that is said to be able to "cure" at ambient conditions. In particular, when the contents of the two packages constituting the composition are combined, the composition is said to consist of a tertiary amine ingredient, a second ingredient characterized as an epoxide ingredient, a third ingredient characterized as an acetoacetoxy ingredient, and a fourth ingredient that is said to possess Michael-reactive double bonds.
U.S. Pat. No. 4,408,018 (to Bartman et al.) notes that the reaction of acetoacetic ester with acrylic acid ester in the presence of a strong base is illustrative of the Michael reaction. Bartman et al. further note that certain "enols" as well as certain "enolates" are known to add across the double bonds of certain alpha, beta-unsaturated ketones and esters. In general, the '018 Bartman patent is directed to crosslinking acetoacetate-type moiety-containing monomer (via the noted Michael reaction) with certain alpha, beta-unsaturated esters. In particular, when tetrabutyl ammonium hydroxide is used as "base", as is disclosed in the '018 Bartman patent, a composition containing the above-discussed, known, mutually-reactive ingredients is said to gel in three (3) hours or less.
Indeed, well-known two-package polymeric surface-coating compositions (or formulations) containing the above-mentioned mutually-reactive ingredients typically gel rapidly, after the mutually-reactive ingredients are combined; and such a "rapid-gelling" characteristic oftentimes renders such known compositions either inappropriate for various applications or simply undesirable. For example, the use of two-package polymeric surface coatings of this sort may give rise to "waste"; and, because of such generation of waste, such two-package compositions may therefore be environmentally less desirable than a single-package composition.
U.S. Pat. No. 3,668,183 to Hoy et al. discloses single-package polymeric surface-coating compositions that include a "blocked" polyamine ingredient as well as a polyacetoacetate or a polyacetoacetamide ingredient that is mutually-reactive with the polyamine. (A ketone or aldehyde is utilized as the "blocking" agent, for the polyamine ingredient.) The various single-package polymeric compositions disclosed in the '183 Hoy patent are typically diluted with conventional solvents. Illustrative solvents include an assortment of commercially-available solvents, wherein such are often characterized as volatile organic compounds ("VOCs"). Typically, water is not included as such a solvent, in the formulation of single-package polymeric compositions. Indeed, as disclosed in the '183 Hoy patent, such single-package polymeric compositions are characterized as being relatively stable, only in the absence of water.
Furthermore, U.S. Pat. No. 4,772,680 (to Noomen et al.) points out that the coating compositions disclosed in U.S. Pat. No. 3,668,183 to Hoy et al. (discussed above) are known to possess certain undesirable properties. For example, Noomen et al. note that the coating compositions of the '183 Hoy patent are known to display certain "unsatisfactory" properties, both to water as well as to certain acids, and unsatisfactory "weathering" properties, when subjected to certain outdoor-exposure conditions.
To distinguish their invention from the '183 Hoy patent, Noomen et al. point out (in the '680 patent) that their invention is based upon liquid coating compositions that include a polyacetoacetate ingredient and a blocked polyamine ingredient which is said to be "different" from the blocked polyamine ingredient that is disclosed in the '183 Hoy patent. In particular, the amino groups of the polyamine ingredient disclosed in the '680 Noomen patent are said to be blocked by an aldehyde or ketone of specified structure; and water is identified as a "suitable" solvent. However, when Noomen et al., in their number of examples, prepare various coating compositions by combining the mutually-reactive polyacetoacetate-containing and "blocked" polyamine-containing ingredients, such compositions are shown to "gel" in 3 hours or less, which is impractical for a number of surface-coating applications.
Thus, a practical single-package polymer-based coating composition, containing the two above-discussed mutually-reactive ingredients--namely, an acetoacetate-type moiety-containing ingredient and an amine moiety-containing ingredient--has not heretofore been able to be made. Yet, a practical, commercially-available single-package coating composition containing these two particular mutually-reactive ingredients is presently in great demand.
For example, European Patent Application 0 341 886/A2 (assigned to ICI Resins BV) discloses an aqueous coating composition that is characterized as a polymer "system" which is said to include a vinyl polymer having chain-pendant amine-functional groups as well as chain-pendant carbonyl-functional groups. Alternatively, the polymer system may include a vinyl polymer bearing a chain-pendant amine-functional group and another polymer molecule bearing a chain-pendant carbonyl-functional group.
Such a coating composition is said to be able to undergo a so-called "self crosslinking" reaction during and/or after coating formation.
It is thought that the "self crosslinking" reaction occurs via the formation of azomethine groups. Chain-pendant amine functionality is said to be preferably introduced into the vinyl polymer via an "imination" reaction, which in turn is said to preferably involve carboxyl (or carboxylate salt) groups of a precursor polymer and an aziridine compound.
Particularly preferred vinyl polymers, which are said to include pendant polymerized units having amine-functional groups as well as pendant polymerized units derived from olefinically-unsaturated monomer, include polymerized units derived from acetoacetoxyethyl methacrylate. Examples 2 and 9 each describe the preparation of an aqueous-based coating composition that was used to produce a film on glass plates. There is, however, no disclosure or even a suggestion in European Patent Application 0 341 886/A2 that these aqueous-based coating compositions possess any storage stability over an extended period of time.
Another example of an aqueous coating composition is disclosed in European Patent Application 0 390 370/A1 (assigned to Imperial Chemical Industries PLC and ICI Resins BV). In particular, European Patent Application 0 390 370/A1 discloses a coating composition--also characterized as "self crosslinkable"--that is said to include at least one polymer having chain-pendant amine-functional groups as well as at least one so-called "non-polymeric" compound having at least two ketone groups that are reactable with the chain-pendant amine groups.
It is thought that the "self crosslinking" reaction occurs via the formation of enamine groups, via elimination of water.
While European Patent Application 0 390 370/A1 discloses that these aqueous-based coating compositions seem to possess 5 weeks storage stability, there is no disclosure or even a suggestion in European Patent Application 0 390 370/A1 that these aqueous-based coating compositions possess any storage stability for an extended period of time such as one (1) year or more.
It is, therefore, clearly presently desirable that there be commercially available a single-package polymeric surface coating composition containing the above-discussed mutually-reactive acetoacetoxy-type functional and amine-functional ingredients. It would further be desirable that such a coating composition be stable over an extended period of time such as 12 months or even longer at room temperature, prior to use.
Moreover, because of the present desire to reduce the total amount of industrial solvents known as volatile organic compounds ("VOCs"), in both consumer and various industrial compositions and formulations, it would be even more desirable that such a single-package composition be water-based as well.